Damping and muffling structure for EL cell

ABSTRACT

A damping and muffling structure for EL cell includes a transparent substrate, a front electrode layer, a lighting layer, an inducing layer, a back electrode layer and an insulating layer. The front electrode layer, lighting layer, inducing layer, back electrode layer and insulating layer are sequentially overlaid on the substrate. A conductive layer is laid between the lighting layer and the inducing layer. The conductive layer is connected to a grounding electrode of a driving circuit, whereby the conductive layer can quickly remove the charge accumulating on the inducing layer so as to minify or even eliminate the vibration and noise of the EL cell.

BACKGROUND OF THE INVENTION

The present invention is related to a damping and muffling structure forEL cell, and more particularly to a damping and muffling structure thatis able to minify or even eliminate the vibration and noise caused byelectromagnetic interference effect (abbreviated into EMI effecthereafter) created by A.C. electric field.

The conventional electroluminescent cell (EL cell) is a thin sheet andmainly used as backlight cell of PDA, mobile phone, etc. FIG. 6 shows aconventional EL cell composed of a transparent substrate 81, a frontelectrode layer 82, a lighting layer 83, an inducing layer 84, a backelectrode layer 85 and an insulating layer 86. By means of a drivingcircuit, an AC voltage is applied to the front and back electrode layers82, 85 to make the lighting layer 83 emit light.

When AC electric field acts on the inducing layer 84, due toelectromagnetic interference effect, the charge will accumulate on theinducing layer 84 to create surface energy conservation effect. Thesurface energy conservation effect will make the charge unevendistribute on the inducing layer 84 and create piezoelectric effect. Thepiezoelectric effect will lead to vibration of the EL cell to emitnoise. This affects the quality of the EL cell or even interferes withthe drive of the LCD module.

In order to solve the problems of vibration and noise of theconventional EL cell caused by AC electric field, generally the EL cellis backed to increase the thickness thereof so as to minify thevibration and noise. Alternatively, the EL cell is tightly attached tothe circuit board to reduce vibration and noise.

However, the EL cell applied to small-size electronic products such asmobile phones is limited in thickness specification. Therefore, thebacking will lead to excessive thickness. On the other hand, the EL cellcan be attached to the circuit board to reduce over 60% noise. However,it is difficult to assemble the module and the use of double-face tapewill lead to increased cost.

SUMMARY OF THE INVENTION

It is therefore a primary object of the present invention to provide adamping and muffling structure for EL cell. The damping and mufflingstructure includes a conductive member, which can quickly conduct thecharge accumulating on the inducing layer to a grounding electrode so asto minify or even eliminate the vibration and noise caused by ACelectric field.

According to the above object, the damping and muffling structure for ELcell includes a transparent substrate, a front electrode layer, alighting layer, an inducing layer, a back electrode layer and aninsulating layer for packaging the EL cell. The front electrode layer,lighting layer, inducing layer, back electrode layer and insulatinglayer are sequentially overlaid on the substrate. A conductive layer islaid between the lighting layer and the inducing layer. The front andback electrode layers and the conductive layer are connected to adriving circuit having a grounding electrode. The conductive layer isconnected to the grounding electrode of the driving circuit, whereby theconductive layer can conduct the charge accumulating on the inducinglayer so as to minify or even eliminate the vibration and noise causedby AC electric field.

The present invention can be best understood through the followingdescription and accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a first embodiment of the EL cell of the presentinvention, showing that the conductive layer is connected to thegrounding electrode;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a plane view showing the structure of a second embodiment ofthe present invention;

FIG. 5 is a plane view showing the structure of a third embodiment ofthe present invention; and

FIG. 6 is a sectional view of a conventional EL cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to FIGS. 1 to 3. The damping and muffling structure for ELcell of the present invention includes a transparent substrate 11, atransparent front electrode layer 12 (which in this embodiment is an ITObus-bar), a lighting layer 13 composed of numerous lighting particles,an inducing layer 14, a back electrode layer 15 and an insulating layer16 for packaging the EL cell. The transparent front electrode layer 12,lighting layer 13, inducing layer 14, back electrode layer 15 andinsulating layer 16 are sequentially overlaid on the substrate 11. Thefront and back electrode layers 12, 15 and the conductive layer 17respectively have three outward extending conductive terminals 121, 151,171 for connecting with a driving circuit 2. A conductive layer 17 islaid between the lighting layer 13 and the inducing layer 14. In thisembodiment, the conductive layer 17 is laid along one side of theinducing layer 14 without affecting the light-emitting region of thelighting layer 13. The conductive layer 17 is connected to the groundingelectrode 21 of the driving circuit 2, whereby the conductive layer 17can conduct the charge accumulating on the inducing layer.

The conductive layer 17 can be made of conductive material such assilver gum, carbon gum, metal and conductive polymer. The less thesurface resistance is, the better the conduction effect is.

The EL cell can be deemed a capacitor sheet. Therefore, when the drivingcircuit applies AC voltage between the front electrode layer 12 and theback electrode layer 15 for driving the lighting layer 13 to emit light,due to EMI effect, the charge will accumulate on the inducing layer 14to create surface energy conservation effect. The surface energyconservation effect will make the charge uneven distribute on theinducing layer 14 and create piezoelectric effect. The piezoelectriceffect will lead to vibration of the EL cell to emit noise.

The conductive layer 17 of the present invention is made of conductivematerial such as silver gum, carbon gum, metal and conductive polymerwhich is able to conduct the charge. In addition, the conductive layer17 is connected to the grounding electrode of the driving circuit 2.Therefore, the charge accumulating on the inducing layer 14 can bequickly conducted to the grounding electrode to weaken the piezoelectriceffect caused by the unevenly distributed charge and minify or eveneliminate the vibration and noise.

It is shown according to the data of an actual test of this applicantthat the noise caused by the EMI effect of the conventional EL cellwithout the conductive member can be heard by human ears. In contrast,human ears can hardly hear the noise emitted by the EL cell of thepresent invention. Therefore, the muffling effect of the presentinvention is apparent.

The above embodiment is only used to illustrate the present invention,not intended to limit the scope thereof. Many modifications of the aboveembodiment can be made without departing from the spirit of the presentinvention. FIG. 4 shows a second embodiment of the present invention, inwhich the conductive layer 37 extends to two adjacent sides of theinducing layer 14. FIG. 5 shows a third embodiment of the presentinvention, in which the conductive layer 47 extends to three adjacentsides of the inducing layer. These can achieve the same effect as thefirst embodiment.

1. A damping and muffling structure for EL cell, comprising atransparent substrate, a front electrode layer, a lighting layer, aninducing layer, a back electrode layer and an insulating layer forpackaging the EL cell, the front electrode layer, lighting layer,inducing layer, back electrode layer and insulating layer beingsequentially overlaid on the substrate, a conductive layer being laidbetween the lighting layer and the inducing layer, the front and backelectrode layers and the conductive layer being connected to a drivingcircuit having a grounding electrode, the conductive layer beingconnected to the grounding electrode of the driving circuit, whereby theconductive layer can conduct the charge accumulating on the inducinglayer to the grounding electrode.
 2. The damping and muffling structurefor EL cell as claimed in claim 1, wherein the conductive layer is madeof conductive material such as silver gum, carbon gum, metal andconductive polymer.
 3. The damping and muffling structure for EL cell asclaimed in claim 1, wherein the conductive layer is laid along one sideof the inducing layer.
 4. The damping and muffling structure for EL cellas claimed in claim 1, wherein the conductive layer is laid along atleast two sides of the inducing layer.
 5. The damping and mufflingstructure for EL cell as claimed in claim 1, wherein the front and backelectrode layers and the conductive layer respectively have threeoutward extending conductive terminals for connecting with the drivingcircuit.